Wireless systems such as the ones based on the IEEE 802.11 standard for indoor local area communication, and the Third Generation Partnership Project (3GPP) based Long Term Evolution (LTE) for terrestrial cellular communication use multiple antennas for transmission and reception, both at an access point (e.g., base-station) and a user terminal (e.g., user equipment (UE)). Multiple-input and multiple-output (MIMO) technology with multiple antennas at a transmitter and a receiver allows for transmitting more than one data stream on the same set of resources (e.g., physical time and frequency resources), thereby significantly increasing data rates over the wireless links with limited transmission bandwidth. Additionally, MIMO systems lead to antenna diversity, which includes wireless diversity schemes that uses multiple antennas to improve the quality and reliability of a wireless link by providing a receiver several observations of the same signal with different channel and interference environment. In other words, if one antenna is experiencing a deep fade, it is likely that another has a sufficient signal. The use of multiple receiver antennas leads to improved receiver diversity, thereby enhancing the received signal quality and reducing the packet error rate. With multiple transmitter antennas, the transmitted signals can be directed to the intended receiver, via transmitter beam-forming techniques, to improve coverage, extend range, and minimize interference caused to unintended receivers.
For UE with a single transmitting antenna, multiple antennas at the base-station (e.g., a single-input and multiple-output (SIMO) configuration) can be used to provide interference rejection capability. An example of spatial-division multiple access (SDMA) includes more than one UE transmits simultaneously to a base-station, and a base-station with multiple receiver antennas, which can jointly decode signals transmitted by the multiple UEs. This simultaneous transmission and joint detection technique can also be referred to as multi-user (MU) MIMO. In MU MIMO, each UE can have more than one transmitter antenna, and more than one transmission stream.